This invention relates in general to a sealing grommet and more particularly to one adapted to be used to seal the base of a pressurized dispensing container.
Pressurized dispensing containers having a piston or collapsible bag that separate pressurized propellant on the underside of the piston or outside of the bag and the material to be dispensed, through a valve, on the upper side of the piston are known in the art. One such pressurized piston operated dispensing container is described in Applicant""s Pat. No. 4,913,323 dated Apr. 3, 1990.
The base of these containers has a small center opening which is used to inject propellant under pressure. The opening has to be sealed thereafter and various grommets or plugs are known to perform this sealing function.
The known grommets or plugs can be dislodged or tilted by a simple fingernail application. For whatever reason, it is known that propellant leakage sometimes occurs with the use of known grommets or plugs.
Because of increased environmental concern with the release of these propellants into the atmosphere, it is desired to provide a grommet which will effectively seal in the propellant and be resistant to the tilting movement or removal that might cause loss of propellant.
Achieving this environmentally desirable result also means a substantial decrease in the number of dispensing containers which fail to achieve targeted shelf life.
Environmental concerns arise out of the use of hydrocarbon propellants such as isobutane, propane and butane. Pressure loss problems arise when using compressed air or compressed nitrogen.
If the sealing plug is disturbed so that some propellant is lost and the propellant has a liquid reservoir, the pressure loss problem may be minor. However, if compressed gas, such a nitrogen, is lost, pressure losses are material and the product cannot all be dispensed.
This invention provides a particular grommet as a sealing plug which is kept in place so as to avoid the problem of pressure loss and also avoid the problem of environmental pollution.
Accordingly, it is the object of this invention to provide a sealing grommet for the base of these pressurized containers which will substantially and effectively reduce the risk of propellant leakage through the base opening.
It is a related object to achieve this sealing object in a grommet design which permits the injection of propellant while the grommet is in place.
The grommet of this invention seals the small opening in the base of a pressurized dispensing container. This container opening is used to charge propellant into the container. The grommet is made of resilient material. The grommet includes a base, a crown and a neck connecting the base and crown.
The neck of the grommet has dimensions which provide an interference fit relationship with the lip of the can opening with which the grommet is to be used. These interference fits assure that the grommet will seal the propellant in the container.
In particular, the height of the neck of the grommet, in its relaxed state, is less than the height of the lip of the can with which the grommet is to be used. In the sealing state, there is an interference fit relationship between the lip on the one hand and the gap between crown and base. The diameter of the neck in its relaxed, unassembled state, is greater than is the diameter of the container opening. When the grommet is assembled on the can, the fit between the neck and the container assures sealing between the grommet and the container opening.
The corner between the neck and the crown is rounded slightly so as to provide a highly effective sealing relationship between this internal corner of the grommet and a corner of an edge of the container opening.
The base has four through openings, through which propellant is charged into the container. In addition, the grommet has a central opening that extends through the base and into the crown. During the charging operation, a pin in the gassing head is inserted through the central opening to push the crown up off the container wall during the propellant charging operation. This causes the extendable neck to decrease in diameter and also serves to hold the crown above the edge of the lip of the container opening. In that state, the four through openings in the base are in communication with the surface of the neck and the interior of the container. Thus propellant can be injected into the lower compartment of the container.
After the propellant charging operation, the gassing head is withdrawn and the resilient neck contracts axially and expands radially bringing the grommet into its sealing state. At that point, the pressure within the container on the top of the crown further assures a tight sealing engagement between the crown and the container bottom.